Cryptology ePrint Archive: Report 2003/241

Hybrid Broadcast Encryption and Security Analysis

Shaoquan Jiang ang Guang Gong

Abstract: A broadcast encryption scheme for stateless receivers is a data distribution method which never updates users' secret information while in order to maintain the security the system efficiency decreases with the number of revoked users. Another method, a rekeying scheme is a data distribution approach where it revokes illegal users in an {\em explicit} and {\em immediate} way whereas it may cause inconvenience for users. A hybrid approach that appropriately combines these two types of mechanisms seems resulting in a good scheme. In this paper, we suggest such a hybrid framework by proposing a rekeying algorithm for subset cover broadcast encryption framework (for stateless receivers) due to Naor et al. Our rekeying algorithm can simultaneously revoke a number of users. A hybrid approach that appropriately combines these two types of mechanisms seems resulting in a good scheme. In this paper, we suggest such a hybrid framework by proposing a rekeying algorithm for subset cover broadcast encryption framework (for stateless receivers) due to Naor et al. Our rekeying algorithm can simultaneously revoke a number of users. As an important contribution, we formally prove that this hybrid framework has a pre-CCA like security, where in addition to pre-CCA power, the adversary is allowed to {\em adaptively} corrupt and revoke users. Finally, we realize the hybrid framework by two secure concrete schemes that are based on complete subtree method and Asano method, respectively.

Category / Keywords: Broadcast Encryption, traitor tracing, copyright management

Publication Info: unpublished

Date: received 20 Nov 2003, last revised 30 Jan 2004

Contact author: jiangshq at calliope uwaterloo ca

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Note: All comments and suggestions are wellcome.

Version: 20040130:174303 (All versions of this report)

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